Even the great detective Hercule Poirot harbours a deep and abiding fear of the dentist, so it is with some trepidation that he arrives at the celebrated Dr Morley's surgery for a dental examination.Yet even Poirot couldn't have guessed that only hours later he would be examining the dentist, dead in his surgery -an apparent suicide.But why would a successful dentist choose to kill himself on such a busy day? Poirot turns to the other patients for answers - but there he finds other, darker questions.

Agatha Christie is known throughout the world as the Queen of Crime. Her books have sold over a billion copies in English with another billion in 100 foreign languages. She is the most widely published author of all time and in any language,outsold only by the Bible and Shakespeare. She is the author of 80 crime novels and short story collections, 19 plays, and six novels written under the name of Mary Westmacott.

Agatha Chrisfie's first novel, The Mysterious Affair at Styles,was written towards the end of the First World War, in which she served as a VAD. In it she created Hercule Poirot, the little Belgian detective who was destined to become the most popular detective in crime fiction since Sherlock Holmes. It was eventually published by The Bodley Head in 1920.

In 1926, after averaging a book a year, Agatha Christie wrote her masterpiece. The Murder of Roger Ackroyd was the first of her books to be published by Collins and marked the beginning of an author-publisher relationship which lasted for 50 years and well over 70 books. The Murder of Roger Ackroyd was also the first of Agatha Christie's books to be dramatised - under the name Alibi- and to have a successful run in London's West End. The Mousetrap, her most famous play of all, opened in 1952 and is the longest-running play in history.

Agatha Christie was made a Dame in 1971. She died in 1976, since when a number of books have been published posthumously: the bestselling novel Sleeping Murder appeared later that year, followed by her autobiography and the short story collections Miss Marple's Final Cases, Problem at Pollensa Bay and While the Light Lasts. In 1998 Black Coffee was the first of her plays to be novelised by another author, Charles Osborne.

One, two, buckle my shoe,

Three, four, shut the door,

Five, six, picking up sticks,

Seven, eight, lay them straight,

Nine, ten, a good fat hen,

Eleven, twelve, men must delve,

Thirteen, fourteen, maids are courting,

Fifteen, sixteen, maids in the kitchen,

Seventeen, eighteen, maids in waiting,

Nineteen, twenty, my plate's empty...